Cut-off valve for engines



@No Model.) 2 Sheets-Sheet 1. J. B. PITGHFORD.

GUT-OFF VALVE FOR ENGINES.

N0. 555,397. Patented Feb 25, 1896'.

No Model.) 2 SheetsSheet 2.

J. B. PITOHPORD. GUT-OPP VALVE FOR ENGINES.

N0. 555,397 Patented Feb, 25, 1896,

ANDREW a GRAHAM PHUTO-UTMQWASHINGTDN 0r:

UNITED STATES PATENT OFFICE.

JOHN B. PITCIIFORD, OF SAN FRANCISCO, CALIFORNIA.

CUT-OFF VALVE FOR ENGINES.

SPECIFICATION forming part of Letters Patent No. 555,397, dated February 25, 1896.

Application filed June 11, 1895. Serial No. 552,393. (No model.)

T 0 (LZZ whom, it may concern:

Be it known that I, J only B. PITCHFORD, a citizen of the United States, residing at San Francisco, in the county of San Francisco and State of California, have invented certain new and useful Improvements in Cut-OE Valves for Engines; and I do hereby declare the following to be a full, clear, and exact description of said invention, such as will enable others skilled in the art to which it most nearly appertains to make, use, and practice the same.

This invention relates to certain new and useful improvements in valve mechanism of engines, and more especially to the cut-offvalve mechanism; and it consists in the arrangement of parts and details of construction, as will be hereinafter fully set forth in the drawings and described and pointed out in the specification.

The object of my invention is to provide a cut-off valve which will enable the engine to run at a high rate of speed with close regulation of the steam, so as to suit the work required and to maintain a uniform number of revolutions, thus overcoming waste in steam and power of the engine.

In carrying out my invention I provide a double-ported evenly-balanced cut-off valve which is so connected with the driving mechanism of the engine as automaticallyto regulate or control the supply of steam to the main steam-valves of the engine in accordance with the work required of the engine, said cut-off valve being so connected as to perform its functions entirely independent of the main steam-valves.

I have shown my invention in the present instance as used in connection with that class or style of steam-engines known as the Corliss engine; but it is not confined to its use in connection with this class of engines, for it may be used to advantage in connection with any style of engines utilizing a main steam or inlet valve.

I In order fully to comprehend my invention, reference must be had to the accompanying sheets of drawings, forming a part of this application, wherein- Figure 1 is a broken side view in elevation of a Corliss engine, showing my valve mechanism connected thereto. Fig. 2 is a top plan view of the mechanism illustrated by Fig. 1.

Fig. 3 is an enlarged detail view in side elevation, partly broken away, of the steam-cylinder, showing the arrangement of the main steam-valves, the exhaust-valves, the cut-off valves for controlling the supply of steam to the main valves, and a portion of the mechanism for operating the said valves; and Fig. 4: is a cross-sectional end view in elevation of the steam-cylinder, taken on line 00 :0, Fig. 3, and viewed in the direction of the arrow,

In the drawings, the letter A indicates the steamcylinder of an ordinary Corliss engine and A the piston cylinder or chamber, within which works the piston B. Above the piston cylinder or chamber is located the steamchest A at each end of which is formed the main-valve chamber B, within which chambers I locate the main steam-valves B Connection is made between the main-valve chambers and the piston cylinder or chamber A through the medium of the port a. Below the said piston cylinder or chamber is located the exhaust-chamber A at each end of which is formed the valve-chamber B Within each of said chambers I secure the rotatable exhaust-valve B and communication is established between said chambers and the piston cylinder or chamber A through the medium of the ports a. The main valves and the exhaust-valves are of such construction as to alternately open and close the ports a at. These features being well known call for no specific description in the present application for Letters Patent.

In front of each main-valve chamber is located the cut-oif-valve chamber C, which valve-chamber communicates with the mainvalve chambers by means of the port I). The cut-off-valve chamber C is provided with two ports 12 12 located opposite to each other, through which ports steam enters from the steam-chest A IVithin the cut-off-valve chambers I locate the cut-off valve C. This cut-off valve, as rotated within the cut-olfvalve chamber, as hereinafter described, opens and closes the ports 1) b the cut-off valve being so constructed as to open or close both ports at the same time. Inasmuch as the steam enters the cut-off-valve chambers through the ports b 12 located directly opposite to each other, it is obvious that there is an even pressure upon the cut-off valve. Consequently the said valve will be at all times evenly balanced. There is a passage-way 12 formed through the cut-ofi valve, so as to connect the upper port, I), of the cut-off chamber with the lower port, 12 and the said passageway is cut away or enlarged at its junction, so as to equal the combined area of the two ports, as shown at b.

The main steam-valves l3 and the steamexhaust valves 13 are connected to the rockplate C by means of the levers C C the outer ends of which levers are connected to the crank-arms cl (1' secured to the outer ends of the valves B 13*, respectively, Figs. 1 and 3. The rock-plate C is secured to and oscillated upon the stud D attached to the side of the cylinder A, and said rock-plate is connected to the fulcrumed standard D by the connecting rod D This fulcrumed standard is connected to the main eccentric D secured to the drive-shaft D of the engine by the eccentric-rod D As the drive-shaft is rotated by any suitable mechanism, the eccentric D is carried therewith, the movement of which throws the eccentric-rod D in and out and causes the fulcrumed standard D to move back and forth, the movement of which oscillates the rock-plate C- and causes the main steam-valves B and the exhaustvalves 13* to rotate or oscillate within the valve-chambers B and B so as to alternately open and close the ports a a.

The rotatable cut-0E valve is connected to the rock-plate E, secured upon the stud D, located behind the rock-plate C by means of the levers E, which are secured at one end to the said rock-plate, the free end of said lever being connected to the crank-arms (l secured to and projecting from the outer end of the rotatable cut-oft valves. Connection is made between the rock-plate E and the fulcrumed standard E by means of the rod E As the fulcrumed lever is moved back and forth, the rock-plate E is oscillated upon the stud D, and through its connection with the cutoff valve causes the same to rotate or oscillate within the valve-chamber C, so as to open or close the ports I) 6 simultaneously, the port or passage-way Z) between the valve-chamber C and the main-valve chamber B being always open.

The f ulcrumed standard E which operates the rock-plate E, is moved back and forth through the medium of the eccentric F, loosely fitted upon the drive-shaft D which eccentric is connected to the said fulcrumed standard by the eccentric-rod F. To the eccentric F is connected the inner end of the short levers ff, the outer ends of said levers being fastened to the inner end of the arms f f respectively, Fig. 1. The outer end of the arms f f I secure to the spokes e e of the governor-wheel G. The governor-wheel is rigidly secured to the shaft D and rotates therewith. The arms f f are connected to the spokes e e by means of the springs 1, 2, the resiliency of which, as the speed of the engine is reduced, draws the said arms inward.

These arms have adjustably secured thereon the weights G. The weighted arms f f will be moved in or out in accordance with the speed under which the governor-wheel revolves. If it is revolved at ahigh rate of speed, the weighted arms will be thrown outward by centrifugal force, while if the governor-wheel is revolved at a low rate of speed the resiliency of the springs 1, 2 will draw the weighted arms inward. As these arms move in or out they impart a corresponding movement to the eccentric F, which in turn moves the fulcrumed standard E through the medium of the eccentric-rod F, forward or backward, the movement of which standard oscillates the rock-plate E and thus rotates or oscillates the cut-off valves. Inasmuch as the cut-off valve is evenly balanced by the pressure of the steam being the same above and below the valve, it is obvious that'the said cut-off valve will be extremely sensitive and rotate with the slightest variation in the speed of the governor, so as wholly or partly to open or close the ports 1) 12 It will be noticed that the cut-ofi-valve mechanism is non-liberating, being at all times in direct communication with the governor. Consequently the movement of the cut-off valve is not only positive, but it is absolutely assured, whether the engine runs under a high or under a low rate of speed, which is not the case where the valve mechanism is automatically liberated at each cut-off movement of the valve.

I am aware that it is not new to provide a single-ported cut-off valve, nor do I wish to be understood as claiming the same as my invention; but I am not aware that it is old to provide a cut-ofi valve capable of closing or controlling two steam-ports simultaneously. Consequently I wish to be understood as claiming this feature.

Having thus described my invention, what I claim as new, and desire to secure protection in by Letters Patent, is

In a steam-cylinder of an engine of the Corliss type, the combination with the pistonchamber, of the steam-chest, the main-valve chambers located at each end of the steamchest and each communicating with the piston-cylinder in order to admit steam at each end thereof, the single-ported rotary main valve located in each main-valve chamber, a double-ported cut-oif-valve chamber communicating with each main-valve chamber by a single port, a double-ported rotary cutofi valve secured in each cut-off-valve chamber for controlling the admission of steam to the main -valve chambers, and of independent mechanism for operating the main valves and the cut-ofi valves.

In testimony whereof I afiix my signature in presence of two witnesses.

JOHN B. PITCHFORD.

Vitnesses W. A. ACKER, LEE D. CRAIG. 

